I am talking about the European copied houses build with self-made cement stones. The prices of cement in Cameroon are at least double as high as in Germany. Considering the fact that the gross income is maybe just one fifth or less the cement becomes extraordinary expansive. I built a house in Bamenda (in fact a local Cameroon company and a Cameroonian architect built it, but we, Alfred and Godwill discussed how to built it in detail.). The house is built with clay bricks. A local company produces them. The clay is mixed with just a bit of cement and then compressed in a hydraulic press. The bricks are very solid. So, there is no need of reinforced concrete beams. The walls do not have to be plastered and they should not be plastered. There is also no need to paint them. They can breathe. They take in water vapor when there is much of it in the house and they give it back when the air in the house is dry. They also keep the house cold when its hot outside and keep it warm when its cold outside. The roof can rest on the gable. So, you can save wood and costs. I decided to cover the whole roof with solid planks which were planed from inside. By doing so the roof becomes very solid. You do not need any ceiling. From inside you have high rooms which look nice. Maybe in a hot place the ceiling will be needed for heat isolation. 

My house was built in a swampy area. Therefore, we built a solid foundation and a water proof bottom plate. In a rocky dry area that is not necessary. It is important to put a layer of tar paper under the walls to prevent water from rising in the walls which will lead to mold in the walls which is harmful to health. It is also advisable to put a layer of semi permeable film on the roof before putting the corrugated iron. In case that there is a leakage in the corrugated iron (which happens quite often) the water will not enter the house and the ceiling will not be spoiled. The costs of that film in Germany are about 1€ per square meter (650CFA).